1. Field of the Invention
The present invention relates to a focus detection apparatus for an autofocus function of an imaging apparatus and, more particularly, to a focus detection apparatus for performing a focus detection of a phase difference method by using an image signal from an imaging element having a pixel for a focus detection in an imaging plane and an imaging apparatus having such a focus detection apparatus.
2. Description of the Related Art
In the related arts, as a focus detection in an imaging apparatus, there is such a technique that a construction for receiving light which passes through different pupil planes of an imaging lens is used for a pixel of an imaging element, thereby performing a focus detection of a phase difference method simultaneously with an image pickup.
For example, in Japanese Patent Application Laid-Open No. 2010-091991, a focus detection is performed by using a plurality of image signals obtained by photoelectrically converting lights which pass through the different exit pupils, by an imaging element having a pixel constructed by one microlens and a plurality of photoelectric conversion units for dividing an exit pupil. At this time, a focus detection operation area is divided and correlation waveforms obtained from the image signals or the division areas are added, thereby adjusting a size of the focus detection area and performing the focus detection saleable for an object.
However, according to the technique disclosed in the foregoing Japanese Patent Application Laid-Open No. 2010-091991, in the case where it is intended to perform the focus detection covering a wider range of an image, it is necessary to increase the focus detection operation area itself. Thus, an amount or data to be processed increases and a scale of a circuit necessary for the arithmetic operation increases. In such a case, there is also such a problem that it takes a time until a final in-focus is obtained.
It is, therefore, an aspect of the invention to provide a focus detection apparatus and an imaging apparatus in which a focus detection covering a wide range is performed onto an image of one frame without increasing a focus detection operation area, and a time which is required to obtain an in-focus in a foots adjustment can be shortened.